The cause of interstitial cystitis is unknown. Much research has focused on two possible causes - a defect in the surface layer of the bladder epithelium and that interstitial cystitis is an autoimmune disease. Bladder surface material, sometimes referred to as "mucin", is poorly characterized. Glycosaminoglycans (GAGs), bloodgroup antigens, epithelial membrane antigen and immunoglobulins are among the substances described in or on the bladder surface. We have obtained material from the surface of the human bladder by irrigation at cystoscopy and by scraping specimens obtained at autopsy. DEAE anion exchange chromatography and SDS- polyacrylamide gel electrophoresis has shown a major band of approximately 28K. Studies of the antiserum to the 28K have shown that it is localized in the surface layer of the urothelium (umbrella cells). The specific aims of the proposal are to determine the relationship of 28K glycoprotein to other known antigens in the bladder epithelium; to characterize the 28K glycoprotein; to prepare monoclonal antibody to 28K; to determine if 28K is altered in the urothelium of patients with interstitial cystitis; to measure 28K in the urine, bladder washings, bladder biopsies and serum of patients with interstitial cystitis; and to study antibody to 28K in the urine, bladder washings and serum of patients with interstitial cystitis. The long term objective of this study is to determine the significance of the 28K component of the bladder surface material in relation to interstitial cystitis. 28K antigen may either protect from disease or autoimmune reaction to 28K may be the cause of interstitial cystitis. It may be possible to influence the pathological course of the disease by altering the amount or nature of the bladder surface material.